Friday, 21 August 2009

More on Windshields

I've spent most of this week working on windshields after my experiments with 2 x layer foil. I've decided that the cone type suits me best and thats what I'd been working on. Ideally the vents would go all the way around the cone but while that may provide the best performance when indoors the vents reduce the cones effectiveness as a windshield when outdoors. I usually try to bias the vents to one side/half of a windshield but even doing so the performance of the stove is badly affected by stiff breezes.

Cone with Vents biased towards the front

Rear of Cone

As I use a 550ml pot rather than the stainless steel pot I used in the previous tests I wanted to optimise performance with my actual cooking set-up.

In addition to the 550ml pot I carry a 375ml mug so I started testing using 350ml water/15ml meths. Using the cone on it's own indoors I managed a boil in 5.54 mins. In an attempt to come up with a repeatable method of simulating a breeze I used a 3 speed pedestal fan set up 1.5 metres from the stove. I checked the windspeed using a cheap anemometer held about 6 inches from the fan, speed 2 on the fan came up at about 5mph, speed 3 at about 8. I'm not sure how this relates to windspeed outdoors but at least it's repeatable.

Trying the cone set-up with the fan set at speed three the fuel ran out prior to reaching a boil, the maximum temperature was about 92 deg. I noticed that even with the vents towards the front of the cone the flame was being blown around too much. I tried the same set up again but with a 2x layer foil windshield around the cone. With the fan set to speed 2 (5mph approx) it actually boiled slightly quicker at 5.49 mins than the cone on it's own in still conditions (fan off) and at speed 3 (8 mph approx) was less than 1 minute slower at 6.38 mins.

I think that makes a secondary windshield worth carrying. The results are laid out below together with a video clip.

I've also included a pic of my cooking set-up. The main pot is a Tibetan titanium 550ml pot which comes with a lid and a Tibetan titanium 375ml mug. The Cone is made to suit my EK meths burner and 550ml pot, the wire mesh potstand allows me to use the smaller mug with the cone. The Plastic container holds a long spoon, teaspoon, cone, foil secondary shield, lighter and home made permanent match together with a measuring cup and the burner.

Cooking Gear unpacked/packed

Time/Temperature Table

Graph Illustrating the Above

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